CN114467134B - Display device - Google Patents
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- CN114467134B CN114467134B CN201980100780.8A CN201980100780A CN114467134B CN 114467134 B CN114467134 B CN 114467134B CN 201980100780 A CN201980100780 A CN 201980100780A CN 114467134 B CN114467134 B CN 114467134B
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- 239000003990 capacitor Substances 0.000 claims abstract description 14
- 239000011159 matrix material Substances 0.000 abstract description 9
- 238000010586 diagram Methods 0.000 description 17
- 230000000694 effects Effects 0.000 description 4
- 230000004048 modification Effects 0.000 description 3
- 238000012986 modification Methods 0.000 description 3
- 241000750042 Vini Species 0.000 description 2
- 238000005401 electroluminescence Methods 0.000 description 2
- 239000002096 quantum dot Substances 0.000 description 2
- 239000010409 thin film Substances 0.000 description 2
- 239000000470 constituent Substances 0.000 description 1
- 230000005684 electric field Effects 0.000 description 1
- 239000010408 film Substances 0.000 description 1
- 230000003252 repetitive effect Effects 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
Classifications
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K59/00—Integrated devices, or assemblies of multiple devices, comprising at least one organic light-emitting element covered by group H10K50/00
- H10K59/10—OLED displays
- H10K59/12—Active-matrix OLED [AMOLED] displays
- H10K59/131—Interconnections, e.g. wiring lines or terminals
-
- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
- G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
- G09G3/22—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources
- G09G3/30—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels
- G09G3/32—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED]
- G09G3/3208—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED]
- G09G3/3225—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED] using an active matrix
- G09G3/3233—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED] using an active matrix with pixel circuitry controlling the current through the light-emitting element
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K59/00—Integrated devices, or assemblies of multiple devices, comprising at least one organic light-emitting element covered by group H10K50/00
- H10K59/10—OLED displays
- H10K59/12—Active-matrix OLED [AMOLED] displays
- H10K59/121—Active-matrix OLED [AMOLED] displays characterised by the geometry or disposition of pixel elements
- H10K59/1213—Active-matrix OLED [AMOLED] displays characterised by the geometry or disposition of pixel elements the pixel elements being TFTs
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K59/00—Integrated devices, or assemblies of multiple devices, comprising at least one organic light-emitting element covered by group H10K50/00
- H10K59/10—OLED displays
- H10K59/12—Active-matrix OLED [AMOLED] displays
- H10K59/121—Active-matrix OLED [AMOLED] displays characterised by the geometry or disposition of pixel elements
- H10K59/1216—Active-matrix OLED [AMOLED] displays characterised by the geometry or disposition of pixel elements the pixel elements being capacitors
-
- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G2320/00—Control of display operating conditions
- G09G2320/02—Improving the quality of display appearance
- G09G2320/0233—Improving the luminance or brightness uniformity across the screen
-
- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G2320/00—Control of display operating conditions
- G09G2320/02—Improving the quality of display appearance
- G09G2320/0238—Improving the black level
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- Engineering & Computer Science (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Physics & Mathematics (AREA)
- Geometry (AREA)
- Computer Hardware Design (AREA)
- General Physics & Mathematics (AREA)
- Theoretical Computer Science (AREA)
- Electroluminescent Light Sources (AREA)
- Control Of El Displays (AREA)
- Control Of Indicators Other Than Cathode Ray Tubes (AREA)
Abstract
In a display region of the organic EL display device, scanning lines (SCAN) are provided in a matrix; a DATA line (DATA) intersecting the SCAN line (SCAN); an initialization line (INI); a subpixel circuit provided so as to correspond to an intersection of the SCAN line (SCAN) and the DATA line (DATA); and an organic EL element (OLED) provided in correspondence with the sub-pixel circuit. The sub-pixel circuit includes: a drive transistor (M2); a write transistor (M1) that connects the DATA line (DATA) to the drive transistor (M2); a capacitor (C1) connected to the driving transistor (M2) for holding the data signal; and a diode-connected transistor (M4) and an initialization transistor (M3) connected between the driving transistor (M2) and the initialization line (INI).
Description
Technical Field
The present invention relates to a display device including a current-driven electro-optical element, and more particularly to an active matrix display device.
Background
Among electro-optical elements constituting pixels arranged in a matrix, current-driven organic EL elements are well known. In recent years, display devices including organic EL (Electro Luminescence: electroluminescence) in pixels have been actively developed, which can make a display device mounted thereon larger and thinner, and which focus on vividness of a displayed image.
In particular, there are many active matrix display devices in which a current-driven electro-optical element is provided in each pixel together with a switching element such as a thin film transistor (TFT: thin Film Transistor) that is individually controlled, and the electro-optical element is controlled for each pixel. This is because, by providing the display device as an active matrix, it is possible to display a higher definition image than a passive display device.
Here, in the active matrix display device, a connection line formed in a horizontal direction for each row, and a data line and a power line formed in a vertical direction for each column are provided. Each pixel includes an electro-optical element, a connection transistor, a driving transistor, and a capacitor. The connection transistor can be turned on by applying a voltage to the connection line, and data can be written by charging a data voltage (data signal) on the data line to the capacitor. The pixel can emit light by turning on the driving transistor by the data voltage charged in the capacitor and causing a current from the power supply line to flow to the electro-optical element.
Accordingly, in an active matrix organic EL display device using organic EL elements, gray scale representation of each pixel is achieved by controlling the current value flowing to the organic EL element of each pixel by the voltage applied to the driving transistor to emit light at a desired luminance. In addition, in the case of displaying an organic EL display device at low luminance, since it is necessary to reduce the current flowing to each organic EL element, a subthreshold region in which the gate-source voltage of the driving transistor is equal to or lower than a threshold value is used.
Prior art literature
Patent literature
Patent document 1: japanese patent application laid-open No. 2014-44316
Disclosure of Invention
Problems to be solved by the invention
However, the subthreshold characteristic of the driving transistor is a region in which a current value abruptly changes due to a change in a gate voltage, and a gate voltage difference for expressing a difference of one gray level may be smaller than a scale value of a data driver supplying a data voltage, and it is difficult to perform good gray level expression. In addition, there are the following problems: gray scale unevenness occurs because gray scale performance of each pixel is affected due to characteristic deviation of the driving transistor.
Accordingly, an object of the present invention is to provide a display device capable of reducing an influence caused by characteristic variations of a driving transistor and realizing excellent gradation expression even at low luminance.
Solution for solving the problem
In order to solve the above-described problem, a display device according to claim 1 of the present invention is characterized in that: scanning the signal line; a data signal line intersecting the scanning signal line; initializing a power line; a subpixel circuit provided so as to correspond to an intersection of the scanning signal line and the data signal line; and a light emitting element provided in correspondence with the sub-pixel circuit, the sub-pixel circuit including: a driving transistor; a write transistor for connecting the data signal line to the drive transistor; a capacitor connected to the driving transistor and holding a data signal; and a diode connection transistor and an initialization transistor connected between the driving transistor and the initialization power line.
According to the above configuration, when initializing the source potential of the driving transistor, since the diode-connected transistor is present in the initialization current path from the driving transistor to the initialization power supply line, the S value of the circuit can be increased. As a result, the relationship between the gate voltage and the current value in the sub-threshold characteristic of the driving transistor is adjusted, and the change in the current value due to the change in the gate voltage becomes gentle. This reduces the influence of the characteristic variation of the driving transistor, and realizes good gradation expression even at low luminance.
The display device may be configured as follows: the diode connection transistor is connected between the initialization transistor and the initialization power line.
The display device may be configured as follows: the diode connection transistor is connected between the driving transistor and the initializing transistor.
The display device may be configured as follows: the initialization power line is connected to a back gate of the driving transistor.
The display device may be configured as follows: the back gate of the driving transistor is connected to the source of the diode-connected transistor.
The display device may be configured as follows: the diode connection transistors are provided in plurality between the initialization transistor and the initialization power line.
The display device may be configured as follows: the diode connection transistor is provided in plurality between the driving transistor and the initializing transistor.
In order to solve the above-described problem, a display device according to claim 2 of the present invention is characterized in that: scanning the signal line; a data signal line intersecting the scanning signal line; initializing a power line; a subpixel circuit provided so as to correspond to an intersection of the scanning signal line and the data signal line; and a light emitting element provided in correspondence with the sub-pixel circuit, the sub-pixel circuit including: a driving transistor; a write transistor for connecting the data signal line to the drive transistor; a capacitor connected to the driving transistor and holding a data signal; and an initialization transistor connected between the driving transistor and the initialization power supply line, and connected between the initialization power supply line and an initialization power supply terminal, a diode connection transistor.
According to the above configuration, when initializing the source potential of the driving transistor, since the diode-connected transistor is present in the initialization current path from the driving transistor to the initialization power supply terminal, the S value of the circuit can be increased. As a result, the relationship between the gate voltage and the current value in the sub-threshold characteristic of the driving transistor is adjusted, and the change in the current value due to the change in the gate voltage becomes gentle. This reduces the influence of the characteristic variation of the driving transistor, and realizes good gradation expression even at low luminance.
The display device may be configured as follows: the initialization power lines are provided in parallel with the data signal lines in a one-to-one correspondence manner, and the initialization power lines are connected to the initialization power supply trunk lines via diode connection transistors provided in a one-to-one correspondence manner to the initialization power lines.
The display device may be configured as follows: the diode connection transistors are provided in plurality between the initialization power supply line and the initialization power supply terminal.
The display device may be configured as follows: the data gate of the initializing transistor is connected to the common scanning signal line with the data gate of the writing transistor.
The display device may be configured as follows: and a scan driving circuit for outputting a driving signal to the scan signal line, wherein the scan driving circuit inputs a driving signal for turning on the writing transistor and the initializing transistor to the scan signal line when the data signal is written, and wherein a source of the driving transistor and the initializing power supply are connected via the diode connection transistor when the data signal is written.
Effects of the invention
The display device of the invention has the following effects: the influence caused by the characteristic variation of the driving transistor can be reduced, and good gradation expression can be realized even at low luminance.
Drawings
Fig. 1 is a pixel circuit diagram showing 1 pixel of the organic EL display device in embodiment 1.
Fig. 2 is a pixel circuit diagram showing 1 pixel of the organic EL display device in embodiment 2.
Fig. 3 is a pixel circuit diagram showing 1 pixel of the organic EL display device in embodiment 3.
Fig. 4 is a circuit diagram of a pixel showing 1 pixel, and shows a modification of the organic EL display device according to embodiment 3.
Fig. 5 is a circuit diagram of a pixel showing 1 pixel, and shows a modification of the organic EL display device according to embodiment 3.
Fig. 6 is a pixel circuit diagram showing 1 pixel of the organic EL display device in embodiment 4.
Fig. 7 is a pixel circuit diagram showing 1 pixel of the organic EL display device in embodiment 5.
Fig. 8 is a pixel circuit diagram showing 1 pixel of the organic EL display device in embodiment 6.
Fig. 9 is a schematic configuration diagram of the organic EL display device in embodiment 6.
Fig. 10 is a pixel circuit diagram showing 1 pixel of the organic EL display device in embodiment 7.
Detailed Description
Embodiment 1
Embodiment 1 of the present invention will be described in detail below with reference to the drawings. In the present specification and the drawings, constituent elements having substantially the same functional constitution are denoted by the same reference numerals, and repetitive description thereof will be omitted. Fig. 1 is a pixel circuit diagram showing 1 pixel of the organic EL display device in embodiment 1.
As shown in fig. 1, an active matrix organic EL display device is provided with: SCAN lines (SCAN signal lines) SCAN, high-level power supply lines ELVDD, and low-level power supply lines ELVSS formed in the horizontal direction for each row; and a DATA line (DATA signal line) DATA and an initialization line (initialization power line) INI formed along the vertical direction for each column. The arrangement direction of the initialization line INI in fig. 1 is set to be the vertical direction, but the arrangement direction of the initialization line INI may be the horizontal direction.
In a display region of an organic EL display device, there are provided in a matrix: a sub-pixel circuit provided so as to correspond to an intersection of the SCAN line SCAN and the DATA line DATA; and an organic EL element (light emitting element) OLED provided corresponding to the sub-pixel circuit. That is, the organic EL element OLED is driven by the sub-pixel circuit. The subpixel circuit includes a write transistor M1, a drive transistor M2, an initialization transistor M3, a diode-connected transistor M4, and a capacitor C1.
The write transistor M1 is provided to connect the DATA line DATA to the drive transistor M2, specifically, the gate of the write transistor M1 is connected to the SCAN line SCAN, the drain is connected to the DATA line DATA, and the source is connected to the gate (DATA gate) which is a control terminal of the drive transistor M2. The driving transistor M2 has a drain connected to the high-level power supply line ELVDD and a source connected to the anode of the organic EL element OLED. The cathode of the organic EL element OLED is connected to the low-level power supply line ELVSS. In addition, a capacitor C1 is connected between the node X and the node Y. Node X is present between the source of the write transistor M1 and the gate of the drive transistor M2, and node Y is present between the source of the drive transistor M2 and the anode of the organic EL element OLED
Between the source of the driving transistor M2 and the initialization line INI, the initialization transistor M3 and the diode-connected transistor M4 are connected in series. In the circuit shown in fig. 1, the initialization transistor M3 is disposed on the side close to the driving transistor M2, and the diode connection transistor M4 is disposed on the side close to the initialization line INI. More specifically, the gate of the initialization transistor M3 is connected to the SCAN line SCAN into which the same SCAN signal as the write transistor M1 enters, the drain is connected to the source of the drive transistor M2 and the anode of the organic EL element OLED, and the source is connected to the drain of the diode connection transistor M4. The source of the diode-connected transistor M4 is connected to the initialization line INI. Further, a structure in which the gate and the drain of the diode-connected transistor M4 are short-circuited and the diode as a transistor is connected is generally known.
In the pixel shown in fig. 1, at the time of data writing, the SCAN line SCAN connected to the SCAN driving circuit is turned on by a SCAN signal (driving signal) to be in a high (H) state, and the initialization transistor M3 and the write transistor M1 are turned on. At this time, since the write transistor M1 is turned on, the capacitor C1 is written with DATA from the DATA line DATA as the both-end voltages of the node X and the node Y.
Further, at the time of data writing, since the initialization transistor M3 is turned on, the source potential of the driving transistor M2 is initialized. At the time of data writing, a current flows in a path (initialization current path) of the high-level power supply line elvdd→the driving transistor m2→the initialization transistor m3→the diode connection transistor m4→the initialization line INI.
When the diode-connected transistor M4 is present in the initialization current path, a voltage drop occurs due to the resistance of the diode-connected transistor M4, and Vy > Vini. Here, vy is the potential of the node Y, and Vini is the potential of the initialization line INI.
That is, in the initialization current path shown in fig. 1, since the diode-connected transistor M4 is present, vgs (gate-source voltage) of the driving transistor M2 becomes small, and thus the current driving capability of the driving transistor M2 is lowered.
During the light emission period of the organic EL element OLED, the SCAN line SCAN is in a low (L) state, so that the writing transistor M1 and the initializing transistor M3 are turned off. At this time, the node X is in a floating state, but since the node X is coupled to the node Y via the capacitor C1, vgs of the driving transistor M2 in the light emission period is kept substantially constant.
The S value (sub-threshold coefficient) of the circuit shown in FIG. 1 is represented by
S＝(1+gm2/gm4)/gm2
To show that the value is (1+gm2/gm 4) times higher than the value of S without diode-connected transistor M4. In consideration of the fact that the initialization transistor M3 is a switching transistor, the transfer conductance of the initialization transistor M3 is much larger than the transfer conductance of the write transistor M1 and the diode-connected transistor M4. Here, gm2 is the transfer conductance of the driving transistor M2, and gm4 is the transfer conductance of the diode-connected transistor M4. That is, if the characteristics of the driving transistor M2 and the diode-connected transistor M4 are the same, the S value becomes 2 times.
In this way, in the circuit shown in fig. 1, by providing the diode-connected transistor M4 on the initialization current path, the S value of the circuit can be increased as compared with the case where the diode-connected transistor M4 is not provided. As a result, the relationship between the gate voltage and the current value in the sub-threshold characteristic of the driving transistor M2 is adjusted, and the change in the current value due to the change in the gate voltage becomes gentle. This reduces the influence of the characteristic variation of the driving transistor M2, and realizes good gradation expression even at low luminance.
< embodiment 2 >
Fig. 2 is a pixel circuit diagram showing 1 pixel of the organic EL display device in embodiment 2.
In the circuit shown in fig. 2, the potential on the source side of the transistor M4 is connected to the back gate input diode of the driving transistor M2, which is different from the circuit shown in fig. 1. In the circuit shown in fig. 2, since the source of the diode-connected transistor M4 is connected to the initialization line INI, the potential of the initialization line INI is inputted to the back gate of the driving transistor M2. Thus, the circuit shown in fig. 2 can further increase the S value.
In the transistor, the data gate refers to a gate electrode to which a data voltage is input, and the back gate refers to a gate electrode formed on the opposite side of the data gate. For example, in the case of a structure in which gate electrodes are formed above and below a semiconductor layer with a gate insulating film interposed therebetween, when a top gate electrode is a data gate, a bottom gate electrode is a back gate, and when a bottom gate electrode is a data gate, the top gate electrode is a back gate. Hereinafter, the data gate is also simply referred to as a gate.
The S value of the circuit shown in FIG. 2 is defined by
S＝(1+(1+a)·gm2/gm4)/gm2
To represent. For simplicity of explanation, if it is assumed that the characteristics of the driving transistor M2 and the diode-connected transistor M4 are the same (that is, gm2=gm4), the S value of the circuit shown in fig. 2 is (2+a) times as high as that without the diode-connected transistor M4. Where a is the back gate control coefficient, more specifically, when the back gate side capacitance of the transistor is set to C BGI Let the driving gate side capacitance be C GI When a=c BGI /C GI To represent. When the voltage Vb is input to the back gate, the threshold of the driving transistor M2 is set as follows
ΔVth＝a(Vb-Vs)
The indicated amount is shifted. At this time, vs is the source potential of the driving transistor M2.
In this way, the circuit shown in fig. 2 can further increase the S value of the circuit as compared with the circuit shown in fig. 1. As a result, the change in the current value due to the change in the gate voltage becomes more gradual, and good gradation expression can be achieved even at low luminance.
Embodiment 3
Fig. 3 is a pixel circuit diagram showing 1 pixel of the organic EL display device in embodiment 3.
The connection order of the initialization transistor M3 and the diode-connected transistor M4 is reversed for the circuit shown in fig. 3 compared to the circuit shown in fig. 1. That is, the diode connection transistor M4 is disposed on the side close to the driving transistor M2, and the initialization transistor M3 is disposed on the side close to the initialization line INI. In the circuit shown in fig. 3, the potential on the source side of the transistor M4 is connected to the back gate input diode of the driving transistor M2.
Since the initialization transistor M3 is present between the diode connection transistor M4 and the initialization line INI in the circuit shown in fig. 3, the threshold variation of the driving transistor M2 due to the potential variation of the initialization line INI disappears, and the luminance of the organic EL element OLED can be stabilized.
Fig. 4 and 5 show a modification of the pixel circuit of the organic EL display device according to embodiment 3.
In the circuit of fig. 3, the potential on the source side of the diode-connected transistor M4 is input to the back gate of the driving transistor M2. If the characteristics of the driving transistor M2 and the diode-connected transistor M4 are assumed to be the same, the S value of the circuit shown in fig. 3 is (2+a) times as compared with the circuit shown in fig. 2 without the diode-connected transistor M4.
On the other hand, in the circuit of fig. 4, the back gate of the driving transistor M2 is not inputted with a potential (the driving transistor M2 does not have a back gate). If the characteristics of the driving transistor M2 and the diode-connected transistor M4 are assumed to be the same, the S value of the circuit shown in fig. 4 is 2 times as compared with the circuit shown in fig. 1 without the diode-connected transistor M4. That is, the S value of the circuit shown in FIG. 4 is represented by the following formula
S＝(1+gm2/gm4)/gm2
To represent.
In the circuit of fig. 5, the potential of the initialization line INI is input to the back gate of the driving transistor M2. If the characteristics of the driving transistor M2 and the diode-connected transistor M4 are assumed to be the same, the S value of the circuit shown in fig. 5 is (2+a) times as compared with the circuit shown in fig. 2 and 3 without the diode-connected transistor M4. That is, the S value of the circuit shown in FIG. 5 is represented by the following formula
S＝(1+(1+a)·gm2/gm4)/gm2
To represent.
Embodiment 4
Fig. 6 is a pixel circuit diagram showing 1 pixel of the organic EL display device in embodiment 4.
The circuit shown in fig. 6 is a configuration in which diode-connected transistors serving as source loads of the driving transistor M2 are multi-layered as compared with the circuit shown in fig. 2. That is, in the circuit shown in fig. 6, 2 diode-connected transistors M41 and M42 are connected between the initialization transistor M3 and the initialization line INI. The number of diode-connected transistors to be multi-polarized is not limited to 2, but may be 3 or more.
In the circuit shown in fig. 6, the back gates of the diode-connected transistors M41 and M42 are input with the source potential of the diode-connected transistor M42 (in other words, the potential of the initialization line INI). By inputting a constant potential to the back gates of the diode-connected transistors M41 and M42 in this manner, the electric field is prevented from being wound, and the saturation of the MOSFET can be improved. This configuration can be applied to the diode-connected transistor M4 shown in fig. 1 to 5. The diode-connected transistors M41 and M42 in fig. 6 may not have back gates.
If the characteristics of the driving transistor M2 and the diode-connected transistors M41 and M42 are assumed to be the same, the S value of the circuit shown in fig. 6 becomes (3+3a+a) as compared with the case where the diode-connected transistors M41 and M42 are not present 2 ) Multiple times. As a result, the circuit shown in fig. 6 can further increase the S value of the circuit, and as a result, the change in the current value due to the change in the gate voltage becomes more gradual, and good gradation expression can be achieved even at low luminance.
Embodiment 5
Fig. 7 is a pixel circuit diagram showing 1 pixel of the organic EL display device in embodiment 5.
The circuit shown in fig. 7 is reverse in connection order of the initialization transistor M3 and the diode-connected transistors M41, M42 as compared with the circuit shown in fig. 6. That is, the diode connection transistors M41 and M42 are disposed on the side close to the driving transistor M2, and the initialization transistor M3 is disposed on the side close to the initialization line INI. If the characteristics of the driving transistor M2 and the diode-connected transistors M41 and M42 are assumed to be the same, the S value of the circuit shown in fig. 7 is also (3+3a+a2) times as compared with the case where the diode-connected transistors M41 and M42 are not present.
The circuit shown in fig. 7 can stabilize the luminance of the organic EL element OLED in the same manner as the circuit shown in fig. 3, in addition to the effect of the circuit shown in fig. 6.
In the circuit shown in fig. 7, the diode-connected transistors M41 and M42 may not have back gates, or the diode-connected transistors M41 and M42 may be connected to the initialization line INI.
< embodiment 6 >
Fig. 8 is a pixel circuit diagram showing 1 pixel of the organic EL display device in embodiment 6.
In the display devices according to embodiments 1 to 5, a diode-connected transistor M4 (or M41 and M42) serving as a source load of the driving transistor M2 is provided in each pixel. However, the source load of the driving transistor M2 need not be located within the pixel as long as it is located on the initialization current path.
The circuit shown in fig. 8 has a connection portion of the diode-connected transistor M4 changed as compared with the circuit shown in fig. 1. That is, the diode-connected transistor M4 is not provided in the pixel but is disposed at the root of the initialization line INI. In other words, the diode-connected transistor M4 is connected between the initialization line INI and an initialization power supply terminal that connects the initialization line INI to the driver IC. Thus, the diode-connected transistor M4 is common to pixels of other rows connected to the same initialization line INI. In the circuit shown in fig. 8, only the initialization transistor M3 is connected between the source of the drive transistor M2 and the initialization line INI. The diode connection transistor M4 may be formed on the same TFT substrate as the pixel circuit, or may be mounted on the driver IC.
In the circuit shown in fig. 8, the initialization current path is configured by a diode-connected transistor M4 which is configured to be a dynamic load on the source side of the driving transistor M2, so that the initialization circuit is a source follower. Thus, when the data voltage is written to the node X in the selected row, the potential of the source (=node Y) of the driving transistor M2 rises by the dynamic load. At this time, the potential of the node Y dynamically rises according to the amount of the initialization current, and thus the slope of the IV curve becomes small.
Here, as shown in fig. 9, it is assumed that 1 initialization line INI exists for each pixel row. In other words, the initialization lines INI are provided in parallel with the DATA lines DATA (not illustrated in fig. 9) in a one-to-one correspondence. That is, if the pixel arrangement is RGB, there is an initialization line INI for each pixel column at R, G, B.
In a frame region (region between a driving region and a driver IC) of the organic EL display device, a plurality of initialization lines INI are connected to the initialization power supply trunk wiring and are common in the row direction. The initialization lines INI for the different columns are independent. Each initialization line INI is connected to an initialization power supply trunk line via a diode connection transistor M4 (referred to as a dynamic load Z in fig. 9). That is, the diode-connected transistor M4 is provided in a one-to-one correspondence with the initialization line INI.
Thus, although the initialization lines INI are common in the row direction, row selection is performed row by row. Therefore, if there are 1 diode-connected transistor M4 (dynamic load Z) at each initialization line INI, it can be used in turn to write the data voltages row by row into the pixels.
In the example of fig. 9, the initialization power supply trunk line and the diode connection transistor M4 are provided in the frame region of the organic EL display device, but the present invention is not limited thereto. For example, the initialization power supply stem wiring and the diode-connected transistor M4 may also be included in the driver IC.
Embodiment 7
Fig. 10 is a pixel circuit diagram showing 1 pixel of the organic EL display device in embodiment 7.
In the circuit shown in fig. 10, as in the circuit shown in fig. 8, a diode-connected transistor is arranged at the root of the initialization line INI. In this case, as in embodiment 4, the diode-connected transistors may be multi-polarized, and the 2 diode-connected transistors M41 and M42 may be connected to the root of the initialization line INI. Of course, the number of diode-connected transistors to be multi-polarized is not limited to 2, but may be 3 or more.
The circuit shown in fig. 10 can further increase the S value of the circuit in the same manner as the circuit shown in fig. 6, in addition to the effect of the circuit shown in fig. 8.
The display devices described in embodiments 1 to 7 are not particularly limited as long as they are devices including a current-driven display element. Examples of the current-driven display element include an organic EL display including an OLED (organic light emitting diode), an inorganic EL display including an inorganic light emitting diode, and a QLED display including a QLED (Quantum dot Light Emitting Diode: quantum dot light emitting diode).
The embodiments disclosed herein are illustrative in all respects and are not to be construed as limiting. Accordingly, the technical scope of the present invention is defined not by the above-described embodiments but by the description of the claims. Further, all changes which come within the meaning and range of equivalency of the claims are to be embraced therein.
Description of the reference numerals
SCAN scanning line (scanning signal line)
ELVDD high-level power line
ELVSS low-level power line
DATA DATA line (DATA signal line)
INI initialization line (initialization power line)
M1 write transistor (part of sub-pixel circuit)
M2 drive transistor (part of sub-pixel circuit)
M3 initialization transistor (part of sub-pixel circuit)
M4, M41, M42 diode connected transistors (part of sub-pixel circuit)
C1 Capacitor (part of sub-pixel circuit)
An OLED organic EL element (light emitting element).
Claims (11)
1. A display device is characterized in that,
the display area is provided with: scanning the signal line; a data signal line intersecting the scanning signal line; initializing a power line; a subpixel circuit provided so as to correspond to an intersection of the scanning signal line and the data signal line; and a light emitting element provided in correspondence with the sub-pixel circuit,
the sub-pixel circuit includes:
a write transistor having a gate connected to the scan signal line and a drain connected to the data signal line;
a driving transistor having a gate connected to the writing transistor and a source connected to the light emitting element;
a capacitor connected to the driving transistor and holding a data signal; and
a diode connection transistor and an initialization transistor connected between the driving transistor and the initialization power line,
the source of the initialization transistor is connected to the drain of the diode-connected transistor, the drain of the initialization transistor is connected to the light emitting element, and the source of the diode-connected transistor is connected to the light emitting element.
2. A display device is characterized in that,
the display area is provided with: scanning the signal line; a data signal line intersecting the scanning signal line; initializing a power line; a subpixel circuit provided so as to correspond to an intersection of the scanning signal line and the data signal line; and a light emitting element provided in correspondence with the sub-pixel circuit,
the sub-pixel circuit includes:
a write transistor having a gate connected to the scan signal line and a drain connected to the data signal line;
a driving transistor having a gate connected to the writing transistor and a source connected to the light emitting element;
a capacitor connected to the driving transistor and holding a data signal; and
a diode connection transistor and an initialization transistor connected between the driving transistor and the initialization power line,
the drain of the initialization transistor is connected to the source of the diode-connected transistor, the drain of the diode-connected transistor is connected to the light emitting element, and the source of the initialization transistor is connected to the light emitting element.
3. The display device according to claim 1 or 2, wherein,
the initialization power line is connected to a back gate of the driving transistor.
4. The display device according to claim 1 or 2, wherein,
the back gate of the driving transistor is connected to the source of the diode-connected transistor.
5. The display device of claim 1, wherein the display device comprises a display device,
the diode connection transistors are provided in plurality between the initialization transistor and the initialization power line.
6. The display device of claim 2, wherein the display device comprises a display device,
the diode connection transistor is provided in plurality between the driving transistor and the initializing transistor.
7. The display device according to claim 1 or 2, wherein,
the data gate of the initializing transistor is connected to the common scanning signal line with the data gate of the writing transistor.
8. The display device according to claim 1 or 2, wherein,
a scan driving circuit for outputting a driving signal to the scan signal line is further provided,
the scan driving circuit inputs a driving signal for turning on the writing transistor and the initializing transistor to a scan signal line at the time of writing the data signal,
when writing the data signal, the source of the driving transistor and the initialization power supply are connected via the diode connection transistor.
9. A display device is characterized in that,
the display area is provided with: scanning the signal line; a data signal line intersecting the scanning signal line; initializing a power line; a subpixel circuit provided so as to correspond to an intersection of the scanning signal line and the data signal line; and a light emitting element provided in correspondence with the sub-pixel circuit,
the sub-pixel circuit includes:
a write transistor having a gate connected to the scan signal line and a drain connected to the data signal line;
a driving transistor having a gate connected to the writing transistor and a source connected to the light emitting element;
a capacitor connected to the driving transistor and holding a data signal; and
an initialization transistor having a drain connected to the driving transistor and a source connected to the initialization power line,
a diode connection transistor is connected between the initialization power supply line and an initialization power supply terminal that connects the initialization power supply line to the driver IC.
10. The display device of claim 9, wherein the display device comprises a display device,
the initialization power lines are arranged in parallel with the data signal lines in a one-to-one correspondence,
the initialization power supply lines are connected to the initialization power supply trunk lines via diode-connected transistors provided in a one-to-one correspondence with the initialization power supply lines, respectively.
11. The display device according to claim 9 or 10, wherein,
the diode connection transistors are provided in plurality between the initialization power supply line and the initialization power supply terminal.
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| PCT/JP2019/038937 WO2021064902A1 (en) | 2019-10-02 | 2019-10-02 | Display device |
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| KR20240114357A (en) * | 2023-01-16 | 2024-07-24 | 삼성디스플레이 주식회사 | Pixel and Display apparatus comprising the pixel |
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| JP6281134B2 (en) * | 2013-01-07 | 2018-02-21 | 株式会社Ｊｏｌｅｄ | Display device, driving device, driving method, and electronic apparatus |
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| KR102461361B1 (en) * | 2016-02-03 | 2022-11-02 | 삼성디스플레이 주식회사 | Pixel, driving method of the pixel and organic light emittng display device including the pixel |
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| US20220367597A1 (en) | 2022-11-17 |
| WO2021064902A1 (en) | 2021-04-08 |
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